Power device having improved feed mechanism

ABSTRACT

A power device having an improved feed mechanism for advancing collated strips of fasteners in sequential fashion to a power actuated driving mechanism.

United States Patent Pomernacki et al;

POWER DEVICE HAVING IMPROVED [56] References Cited UNITED STATES PATENTS3,099,837 8/1963 Heilman, Jr ..2'27/ I36 2,928,094 3/l960 Crooks =1al..... .227/136 x 3,353,737 11/1967 Howard =1 :1]. ..227/l36 3,563,4382/1971 Doyle ..227/13e x Primary E.\'am1'uer-Granville Y. Custer. Jr.Armrne \--Robert W. Heart, Michael Kovac and Jack R. Halvorsen [57]ABSTRACT A power device having an improved feed mechanism for advancingcollated strips of fasteners in sequential fashion to a power actuateddriving mechanism.

6 Claims, 14 Drawing Figures M /2e4 266 ,1 \94 1 W PATENTEBMAY 9 I972661 ,3 1 3 SHEET 1 0F 5 INVENIO gs Henry Pomemqc 1 r E Scmr/ Thai! an yaINVEN7 OR s Pomemqclr/ O/lver E. Soon Henry T/mir AH 'ys PMENTEDMM 91972 SHEET 3 OF 5 MAY 9| PATENT We 3,551,313

SHEET b UF 5 INVENTORS Henry Pamernaclr/ r E. Saar/ POWER DEVICE HAVINGIMPROVED FEED MECHANISM BACKGROUND OF THE INVENTION Feed mechanisms usedfor moving collated strips of fasteners to a power driving device whichhave been heretofore used, have generally incorporated either positivedrive mechanisms that are powered by suitable means such as sprocketwheels to position a fastener at a predetermined point for driving oralternatively, have employed a spring means and a pusher rod acting onthe far extremity of the collated strip remote from the driving means toposition the foremost fastener against a stop or other suitable meansfor locating individual fasteners relative to the driving means. Each ofthese devices has had its own inherent problems relative to jamming orinsufficient power to actuate the strip. Still other devices haveutilized gravity feed or vibratory feed tomove individual fastenersalong a pair of rails which supported the fasteners by their head orother suitable flange means. This form of means had the inherentdifficulties of supply of fasteners at a predetermined location at apredetermined time.

SUMMARY The present invention relates to a power tool having a feedmechanism for advancing a collated strip of fasteners in sequentialfashion with the strip being in the form of individual carrying memberswhich support the fastener at its'head and at its tip and with the upperor end portion of the individual supporting means being joined to thenext adjacent supporting means. The feed means contemplated by thisinvention include a pair of rails supporting the collated strip,oscillating finger means for advancing the strip a predetermineddistance, power means for actuating the finger means, movable first stopmeans for interrupting movement of said strip along said track, andsecond movable stop means for controlling actuation of the advancingmeans said predetermined distance.

The actual powered driving mechanism is utilizable as the movable firststop means so that when the powered driving means is in its extendedposition, the collated strip is prevented from advancing along thetrack. The second movable stop means is actuated by the same poweroperating source which actuates the powered driving means so that theadvancing means is prevented from moving the strip until such time asthe powered driving means is actually placed in operation at which timethe second movable stop means permits advancement of the strip againstthe powered driving means as it is being retracted to its cocked oroperable position. When the driven power means is removed from the pathof the track, a supporting member for an individual fastener in thecollated strip is moved to the predetermined position for acceptance ofthe blow by the driven power means.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of apreferred embodiment of the invention showing it being gripped by anoperator;

FIG. 2 is a side elevation in partial section of the preferredembodiment of the invention;

FIG. 3 is a side elevation in partial section of the power unit used bythe invention with the power drive piston in extended position;

FIG. 4 is a front elevation in partial section of the power unit shownin FIG. 3 with the power drive piston in retracted position;

FIG. 5 is an enlarged partial section of the accumulator piston, theupper end of the power drive piston, and the brake of the device shownin FIGS. 24;

FIG. 6 is a partial bottom end view in section taken along line 6-6ofFIG. 5;

FIG. 7 is a side elevational view of a second embodiment of theaccumulator piston;

FIG. 8 is a front elevational view of the device shown in FIG. I;

FIG. 9 is a front elevational view in partial section similar to theview in FIG. 4 but with the power drive piston in extended position andhaving the cut-off mechanism mounted on the side thereof, taken alongline 9-9 of FIG. 2;

FIG. 10 is an expanded perspective view of the elements of the controland cut-off mechanism;

FIG. 11 is partial sectional view, from the bottom of the invention asviewed in the drawings along line -11 in F IG. 2, showing a portion ofthe control means of FIG. 10 in operative relationship to the switchmeans being controlled;

FIG. 12 is an end view of the device shown in FIG. 2 as viewed from theright-hand end of that drawing;

FIG. 13 is a partial sectional view taken along the line l3 13 in FIG.2; and I FIG. 14 is a perspective of the feeder finger means.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawingswherein similar parts are designated by similar numerals, the inventioncontemplates a new and improved portable power tool with a cylinder bodyforming a power unit including a reservoir in which a compressible fluidis maintained under pressure. An accumulator piston and a drive pistonpositioned in said cylinder are simultaneously movable to retracted orcocked positions by the introduction of a non-compressible power fluidinto the cylinder in which the pistons are reciprocably movable with thepower fluid acting on exposed areas of the drive piston to move it withthe accumulator piston until the drive piston reaches its fully cockedposition whereupon further movement of the accumulator piston exposesadditional areas of the drive piston to pressure of the power fluid. Atthis point the compressible fluid acting through the accumulator pistonupon the power fluid in the cylinder imparts drive movementto the drivepiston. The device is fully operable only when it is properly positionedwith respect to a workpiece or structure. The tool has means fordeactuating a pump used to supply the noncompressible power fluid,before the drive piston reaches its fully cocked position, if the powerdevice is not so properly positioned; The drive piston and the bodycylinder include cooperable means for slowing or braking the movement ofthe drive piston as it approaches its fully extended position tominimize shocks to the body particularly when the power of the drivepiston is not utilized for driving an object, such as a fastener, butrather is actuated in free flight. An automatic recycling feed means isprovided which is sequentially operated during each operation of thepower device. The feed means generally acts upon a collated strip ofdevices which are to be sequentially acted upon by the power device.Further, there is provided a cut-off mechanism for eliminating portionsof the collating means used for holding the devices to be acted upon bythe tool.

Thus, the device generally includes the power device having a combinedmechanical-electrical control means 22, a feed means 24, and a cut-offmechanism 26.

POWER SOURCE The power device 20 includes a stepped body portion havinga central pass-through bore 32 of a predetermined diameter. The bore 32is provided with a plurality of counterbores 34, 36, 38, and 42 whichare each progressively larger diameters for ease in assembly of variousitems coaxially within the bore. Counterbore 34 accepts a metallicsleeve bearing 44 while counterbores 36 and 38 accept bearings 46 and 48respectively with a sealing member 50 being sandwiched between the twobearings and restrained thereby against axial movement. Radially offsetin body 30 from the central bore 32 is an axially extending fluidpassageway communicating with the lower extremity of counterbore 40, asviewed in FIGS. 2 and 3, and having a pair of lateral ports 62 and 64,for purposes best set forth hereinafter.

A cylinder provided at one end with an external threaded portion 72 isthreaded into counterbore 42 with its mating threads 52. The cylinder70, adjacent said one end, has an annular recess adapted to accept anO-ring sealing member 74 for sealing engagement with an unthreadedportion of the side wall of counterbore 42. The cylinder has a bore 76including a taper 78 at its lower extremity, adjacent said one end, andan enlarged cavity at its opposite or upper extremity forming a chamber80. The upper end of the chamber 80 is threadedly apertured to accept amating threaded cap 82 and further includes a recess 84 for acceptanceof an O-ring seal 86 which is compressibly captured between the flangeof cap 82 and the end wall portion of chamber 80. The cap 82 iscentrally apertured and provided with a cylindrical extension 88 whichis tubular in form and extends into the chamber 80 for a substantialportion of the axial extent of chamber 80. A valve means 90 ispositioned within the bore of the cap 82 and communicates with chamber80 for purposes best set forth hereinafter.

Positioned within the bore 32 is the power drive piston which includes apreferably cylindrical central portion 102 and enlarged upper endportion 104, cylindrical in form and connected to the central portion102 by an upwardly and outwardly tapering portion 106. At the oppositeend of central portion 102, the drive piston is provided with a groove108 forming a shoulder 110 which faces towards the enlarged end portion.The balance of the lower end of the drive piston 100, in the illustratedembodiment, is a generally reduced cylindrical portion or hammer 112smaller in diameter than the bore 32 and preferably hardened to serve asthe hammer or power impacting portion of the drive piston. The bearingmembers 44, 46, and 48 are so dimensioned relative to the centralportion 102 of the drive piston 100 as to laterally support the deviceduring its axial movement within the bore 32 and into retracted positionwithin cylinder 76. The seal 50 provides a sliding seal which preventsegress of fluids around piston 100 between bore 32 and cylinder 76.

The upper end surface of the enlarged end portion 104 of piston 100 isrecessed to form an open end chamber 114 having a bottom wall 115 andside walls 116 which are frustoconical in configuration and have theirwidest diameter at the free or open end ofthe chamber.

Positioned within the cylinder bore 76 is a free floating accumulatorpiston 120 having annular recesses intermediate its extremities toaccept the seal 122 and lateral circumferentially disposed bearing means124 and 126. The seal 122 is preferably a lip seal for slidingengagement with the bore 76 and may be manufactured or urethane. Due tothe physical properties of urethane the lip seal 122 is reinforced by abumn O-ring 128 to provide additional stability to the lip seal 122.Stability of the accumulator piston 120 within cylinder 76 is enhancedby the bearings 124-126 which preferably are ofthe self-lubricatingvariety. They may be fabricated from a lubricious plastic material suchas those commonly sold under the tradenames ofnylon or Teflon." Acylindrical projection 130 extends from the lower end of the accumulatorpiston 120 and is so dimensioned as to be accepted within thefrustoconical wall configuration 116 of the open end chamber 114 locatedin the enlarged head or end portion 104 of the drive piston 100. Thejuncture between the extension 130 and the side wall 116 intermediatethe axial extremities of wall 116 forms an effective seal and yetpermits axial separation between the members under specific conditionswhich will be set forth hereinafter.

Located complimentarily within counterbore 40 and surrounding the drivepiston 100 is a brake mechanism which includes a body 142 having acentral throughbore 144 with a complimentary shape slightly larger by afew thousandths of an inch than the central portion 102 of piston 100,this difference in size being overaccentuated in the drawing for clarityof illustration. An enlarged counterbore 146 is joined in the bore 144by two frustoconical wall portions 148 and 150 each having a differentincluded angle, portion 148 having an angle of approximately 30 measuredrelative to the axis of bore 144, while piston 150 has an angle ofapproximately 15 measured relative to the axis of bore 144. Thecounterbore 146 is extended axially beyond the one extremity of body 142by means of the flange 154 which has an outer frustoconical wall 156,having an included angle slightly greater than taper 78 to provide anupwardly opening throat 157, as viewed in FIG. 5, between the facingsurfaces of the two members. The opposite extremity of body 142 as bestseen in FIG. 6, is provided with a plurality of grooves which extendradially from an annular counterbore 162 forming a recess around thedrive piston central portion 102 when positioned within bore 144. Theside wall of the body 142 is provided with a plurality of flats 164which each form a recess 166 extending axially between the brake body142 and the counterbore 40 of main body portion 30. The end of the sidewall adjacent grooves 160 is chamfered as at 167 to form an annularchamber 168 between the brake 140 and the bottom wall of the counterbore40, while at the same time, providing communication between the axialchambers 166 formed by the flats 164 and the grooves 160. The axialextent of brake body 142 is slightly greater than the axial extent ofcounterbore 40, whereby the body 142 extends into counterbore 42 formingan annular cavity 169. The lower extremity of cylinder 70 when screwedin tightly bears against the upper wall 143 of brake body 142. Cylinder70 further is provided at its free end with a plurality of grooves 79which are generally radially extending and communicate with cavity 169.Thus, free access is provided for fluids introduced through bore 60 tothe chamber 168 for passage either through grooves 160 and counterbore162 thence upwardly between piston 100 and bore 144, into contact withthe undersurface of portion 106 or, from chamber 168 through axialrecess 166 into chamber 169 and thence through grooves 79 and throat 157into contact with the exposed undersurface area 129 of accumulatorpiston 120, as will be further discussed hereinafter.

Intermediate the extremities of the body 30, a pair of oppositelydisposed slots 170 communicate between the exterior and the bore 32. inthe preferred embodiment, the body 30 has an enlarged upper section anda reduced lower portion and the slots 170 are generally positioned atthe juncture between these two sections. Positioned within slots 170 area pair of fingers 172 each being rotated at one end on a pin 174 mountedin the enlarged upper section. Each finger 172 has an abrupt shoulder176 at its opposite extremity. Adjacent to shoulder 176 is a sliding orcam surface 178 adapted to ride on the central portion 102 of the piston100 and with the abrupt shoulder 176 adapted to cooperate with theshoulder 110 of the drive piston 100. A leaf spring 180 is fastened by arivet or screw 182 at one end and at its opposite or free end 184 bearsagainst each of the fingers 172 to serve as a biasing means to urge thefingers 172 into engagement with the piston and its associated shoulder110. The fingers 172 effectively control the upper limit oftravel of thepiston 100 while permitting free movement of the piston to an extendedor lower portion, as viewed in the drawings. It will be apparent thatother means such as spring loaded balls or plungers that can behydraulically or spring actuated will operate effectively as a stopmeans.

At the free end of the body 30 adjacent bore 32, there is provided anose piece 190, having a tapered lower portion 192 adapted to permitentry of the tool into confined spaces. The upper portion of nose pieceisdefined by a pair of flanges 194 which are apertured for acceptance ofa pair of bolts 196 for fastening of the nose piece in embracingrelation to the body 30. The interior of the nose piece is furtherdefined by a fore and aft passageway having a pair of opposed verticalside walls 198 and lower inwardly tapering portions 200 which meet in aradiused section 202 on the vertical axis of the nose piece. At theupper end of the passageway defined by walls 198 a track means ispositioned and defined by oppositely extending grooves 204, whilecentrally of the nosepiece 190 there is located a vertical bore 210which traverses the fore and aft passageway. This particular nose piecewas designed to accept a collated strip 216 of fasteners 217 shown inphantom in which the collating means 216 includes individual plasticelements or holders having laterally extending head means adapted toride in track 204 and a body portion adapted to position a fastener 217held by the collating means in coaxial position with the drive pistonwithin the bore 210. The bore 210 has a dimension sufficiently large toaccept the hammer portion 112 of the drive piston 100 plus the materialthickness of the collating means.

In the operation of this power source several physical relationshipsmust be kept in mind. The area of the face or surface 115 of the pistonhead, defined by the frustoconical wall 116, is greater than thecross-sectional area of the drive piston 100 at the seal 50 so that whenthe side wall 116 seals between the projection 130 on the accumulatorpiston and the drive piston head, any fluid pressure which is exerted onthe drive piston tends to move the piston head toward the accumulatorpiston and hold it in tight engagement therewith. Accordingly, fluidpressure introduced through port 62 into the bore 60 of the body andthence through the chamber 168, grooves 160 and bore 144, when theaccumulator piston and the drive piston are in the position illustratedin FIGS. 2, 3, 5 and 9, will tend to force the drive piston head intoengagement with the accumulator piston 120 and tend to move the drivepiston 100 upwardly as seen in these figures.

Compressed gas is introduced into the power accumulator or compressedgas chamber 80 through valve 90. It will be ap parent that when thechamber 80 is charged with a gas under pressure, the accumulator piston100 will be forced downwardly, as seen in FIG. 3, to tend to hold thedrive piston in the position illustrated in FIG. 3, and with theprojection 130 moved into sealing relationship with the frustoconicalside wall 116. The compressed gas charge that is introduced throughvalve 90 normally has a pressure of approximately 2,000 p.s.i. Asuitable gas for use in a device of this type is nitrogen, althoughother forms of non-explosive, compressible gases can be used with equalfacility.

To cause the operation of the power source to perform some work, such asthe driving of a nail, a non-compressible fluid is introduced from areservoir by a pump, neither of which are shown, but which are wellknown in the art,'through the port 62 into the bore 60 and thencethrough the various passageways into the clearance between bore 144 inthe central body portion 102 of the drive piston 100, into engagementwith the undersurface 106 of the head 104 of the drive piston. As thepower fluid is pumped into the main bore, it causes the accumulatorpiston 120 and the drive piston 100 to be moved upwardly as seen in FIG.3. The drive piston is caused to move upwardly with the accumulatorpiston since, as was explained above, the area of the surface 115, aswell as the area of the tapered portion 106 of head 104 is greater thanthe cross-sectional area of the piston 100 at the seal 50 so that thefluid pressure acting on the drive piston tends to force the drivepiston toward the accumulator piston. Continued introduction of thepower fluid to the bore forces the accumulator piston 120 and the drivepiston 100 to move upwardly toward the fully retracted positions thereofillustrated in FIG. 4 against the force exerted by the compressed gas inthe power accumulator or chamber 80. The drive piston and theaccumulator move upwardly until the fingers 172 bring their associatedshoulders 176 into engagement with the shoulder 110 on the drive piston100. At this time, the drive piston is in its fully retracted or cockedposition. The accumulator piston, how-- ever, is free to continue suchmovement as the pumping of the power fluid continues. Such separation,as seen in FIG. 4, separates the seal between the projection 130 and theside walls 116. Once this seal is broken, the pressure of the powerfluid is now exerted across the whole cross-sectional area of the face115 of the drive piston head 104 and as a result, the drive piston isnow moved forcibly and with great velocity downwardly due to the forceexerted by the compressed gas of the power fluid in the main bore of thecylinder 76. Since the power fluid is non-compressible, it serves as alinkage or transfer means for the force being exerted by the compressedgas through the power fluid against the head 104 of the drive .piston100. The accumulator moves behind and follows the drive piston but sinceit extends across the full cross-sectional area of the bore of thecylinder; it moves at a slower speed than the drive piston. Such rapidmovement of the drive piston, of course, drives the nail or otherfastener into the workpiece or structure.

The frustoconical portion 106 at the undersurface of head 104, isdisposed at an angle of approximately 30 to the vertical axis of thepiston 1 10. This frustoconical shape of the head 104, causes the headto tend to trap power fluid in the reduced annular shape of bore 146 andthence against the double frustoconical counterbore 148-150.Additionally, as the head progresses down the cylinder 76, the powerfluid tends to be forced outwardly through the throat 157 and theassociated passageways communicating therewith.'As a result, theentrapment of the power fluid between frustoconical face 106 and thereduced bore 146 and its associated counterbores 148-150, slows down thedrive piston as it approaches the end of its power stroke and cushionsthe shock of the engagement between the head 104 and the brake 140. Theaccumulator piston 120 is now spaced from the drive piston head due tothe presence of the additional power fluid which has been pumped intothe cylinder 76. The pump, of course, may continue to pump during theworking or driving stroke of the drive piston, but the movement of thedrive piston is primarily due to the force exerted by the compressed gasin the chamber which is transmitted through the accumulator piston tothe power fluid, acting as a linkage, against the surface 115.

The power fluid in front of the accumulator piston is now forced by thepressure of the compressed gas in the chamber 80 and the cylinder 76, tomove backwardly through the various passages into the bore 60 and outthe port 62 into the reservoir, not shown. As a result, the accumulatorpiston moves downwardly until its extension 130 once again engages thewall 116 of the drive piston head and again provides a seal between thehead 104 and the accumulator piston 120. The power source is then againin condition for another cycle of operation.

It will now be apparent that the power source illustrated and describedperforms work due to the expansion of the compressed gas in the poweraccumulator or gas chamber 80 and cylinder 76. The pressure of the gasintroduced into the gas chamber 80 may be initially of a relativelylarge value, say 2,000 per square inch, and with the further compressionof the gas in the chamber 80, due to the movement of the accumulatorpiston 120 in the cylinder 76 by the non-compressible power fluid,causes it to attain a pressure of a still higher value, say 4,000 poundsper square inch, while the power fluid will reach 6,000 p.s.i. at thetime of separation between the power piston and the accumulator piston.Thus, the energy stored in the compressed gas is employed to drive thepiston, using the power fluid as a linkage between the accumulatorpiston and the drive piston, and thus perform such functions as thedriving of a fastener into a workpiece. Normally, the volume of thedrive piston in its axial movement of approximately 4 inches is equal tothe volume of the accumulator piston in its movement of l to 1% inchesduring the power stroke. The power fluid is virtually non compressibleand has approximately the same displacement. It should be noted that theextension 88 of the cap 82 serves as a safety device to prevent movementof the accumulator piston 120 out of the cylinder bore 76 into the poweraccumulator or gas chamber 80. Thus, the piston 120 is maintained in itsoriented position within the cylinder 76, as well as preventingover-compression of the gas within the chamber 80 by providing a stop tothe axial movement of the piston 120 after separation from piston whenit contacts the lower extremity of the tube 88.

It has been found occasionally that the seal 122 under the pressuresdeveloped, permits passage of the power fluid into cylinder 76 andcomingles it with the compressed gas. Due to the heat generated in thecompression of the gas, the power fluid is atomized and can produce anundesirable condition.

To this end, a second embodiment of the accumulator piston is shown inFIG. 7, wherein similar parts are designated by similar numerals withthe addition of the suffix a. This embodiment includes virtually a onepiece double piston, including portion 120a having a single seal 122a,and the forward projection 130a adapted to seal with the cavity in theend of head 104 in the same fashion as the first embodiment. Thisembodiment includes an extension 220 provided with a circumferentialcavity 222 for acceptance of a second seal 224. At the juncture betweenextension 220 and the basic portion 1200, there is provided a pluralityof transverse passageways 230 which communicate between the periphery ofthe piston and a central bore 232 which opens through the opposite endof extension 220. The open end of bore 232 is closed by a threaded plug234 having a central pass-through bore 236 providing limited ingress andegress to the bore 232. Positioned within bore 232 is a free floatingpiston 240 having an annular groove adapted to accept an O-ring seal242. The free end 244 of piston 240 is conically shaped and adapted tointersect and close the passageways 230 communicating with the peripheryof the embodiment. In the operation of this device in the environmentpreviously described, it will be appreciated that the compressed gasesfrom chamber 80 will pass through the bore 236 and act upon the end ofthe piston 240 to maintain it in the seated position shown in FIG. 7. Inthe event that the power fluid should by-pass seal 122a, it will seekthe passageway 230 and act against the relatively small diameter piston240 to move the piston to the right, as viewed in FIG. 7, against thecompressed gas and to form a reservoir within the bore 232. The relativecross-sectional areas of piston 240 and seal 224, are such that thepiston will be acted upon more readily by the power fluid than the sealand thus the power fluid will be prevented from passing into thecylinder 76 and chamber 80 to comingle and atomize with the compressedgas.

The power source previously described is fitted in the illustratedembodiment to a body shell 250 having a central aperture 252 defining ahand grip portion 254. A rear aperture 256 is adapted to acceptappropriate fittings 258 for the acceptance and mounting of tubularmeans 260 carrying the power fluid from its reservoir and supply pump,not shown, to the port 62. Also positioned in casing 250 at its rear orrighthand end, as viewed in FIG. 2, are terminal means 264 for providingelectrical access to the control cable 266 on the exterior and internalwiring 268 on the interior of the casing for control of the externalpump and its supply of power fluid to the power source. Other details ofthe casings in body 250 will be described hereinafter with reference tothe specific features being described.

CONTROL MEANS In the operation of the power source, it is necessary toprovide mechanical detection means which will insure that the tool is inthe proper position for operation prior to the power stroke by thepiston. Additionally, control means are provided which areinterconnected electrically with the mechanical detection means forpurposes of remotely controlling the pump and reservoir which arelocated at a distance from the power tool. Further, means must beprovided for controlling the position of the extreme end of the hammerportion 112 relative to the workpiece since the extended position of thehammer extremity is a definite physical relationship relative to thelower end of the nose piece upon the completion of the power stroke andthe extension of the power piston 100 internally of the body.

As best seen in FIGS. 1, 2, 3, 8 and 10, there is provided a flat frontface 31 on the lower portion of body 30, adapted to accept a detectorblade 270 in sliding superposed relationship thereto. Detector blade 270is basically a rigid, flat structure having a lower cutout portion 272at one end which is greater than and generally complimentary incross-sectional configuration to the passage through the nosepiecedefined by walls 198 and 200. The exterior edge surface at said one endof plate 270 forms a nose or reduced section 274 generally complementaryto the sloping wall 192 of the nose piece and terminating in a flatsurface 276 at its free extremity for contact with the work surface. Apair of lugs or dogs 278 extend laterally from opposite side edges ofthe blade 270 intermediate their extremities. An aperture 280, generallyrectangular in shape, is positioned centrally and intermediate theextremities of the blade. The opposite or upper end 282, as best seen inFIG. 10, present a cammed or sloped surface which is non-perpendicularto the side edges of the blade. End 282 is adapted to cooperate withmovable plate 284, as best seen in FIG. 8, having an elongatedtransverse aperture 286 and a retaining screw 288 affixed to the frontface 31. Lateral adjustment of plate 284 will, in cooperation withsurface 282, determine the extent of movement of the detector blade 270in an upward direction, as viewed in the drawing, along the front face31. An elongated cavity 290 is provided in face 31 and adapted to accepta spring member 292 having a diameter substantially equal to thecombined measurement of the thickness of the blade 270 and the depth ofthe cavity 290. After spring 292 is positioned within the cavity 290,the blade 270 is positioned with the spring member located within theaperture 280. A flat cover plate 300 is positioned over the blade 270and the assembly maintained in place by lateral flanges 302 extendingrearwardly from plate 300 and secured to the body 30 by suitable meanssuch as a screw 304 and nut 306. The cover plate 300 maintains the blade270 in free sliding relationship to the front face 31 with the spring292 centering the blade 270 when forces tending to move the blade ineither direction have been removed. The lower extremity of blade 270defined by surface 276 normally extends beyond the free extremity ofnose piece before contact with a workpiece.

The effects of movement of the detector blade upwardly against spring292 when contacting a workpiece are translated into useable impulse bymeans of a pair of levers 310 and 312 mounted on opposite sides of body250. The lever 310 has a forward portion 314 terminating in a cammedbulbous tip 316 adapted to be accepted between the adjacent side lugs278. Lever 310 is provided with a central pivot point aperture side lugs278. Lever 310 is provided with a central pivot point aperture 318 and arearwardly extending arm 320 terminating in a laterally extending flange322 having a cammed surface 324 adjacent its lower edge, as viewed inFIGS. 2 and 10. Lever 312 is provided with a forward portion 330 and asimilar bulbous tip 332 for acceptance between the lugs 278 on theadjacent side of 270. Intermediate the extremity of lever 312, there ispositioned a stud 334 at its pivot point and adapted to be acceptedwithin the pivot point aperture 318 of the lever 310.

Within the case 250 there are positioned two switches 340 and 342.Switch 340 is provided with a spring pivot arm 344 adapted to be incontact with the cam 324 of lever 310. In the upper portion of casing250, there is provided in the hand grip aperture 252 a trigger switchlever 350 pivoted at 352 and having an upwardly extending lever 354. Theswitch trigger 350 is adapted to act against adjustable spring 356 whenan upward pressure is brought to bear on trigger 350, as viewed in FIG.2, to swing flange 354 into contact with switch 342. Switches 340 and342 are connected in series internally of the casing by appropriatemeans with the cable 268. When the trigger 350 is squeezed, switch 342is closed, but the circuit will not be complete unless the detectorblade 270 is moved upwardly, as viewed in FIG. 2, so as to pivot lever310 and move the cam surface 324 downwardly to actuate switch 340 andthereby close the series circuit. If pressure against the nose 276 ofblade 270 is removed, as by removal of the tool from the work surface,the circuitry will be opened and electrical power to the pump whichsupplies the power fluid will be cut off and the power stroke will beunable to proceed in its cycle. Thus, the too] must be in apredetermined position for driving, as well as having the trigger 350depressed in order to carry out its sequence of firing.

CUT-OFF MECHANISM The collated strip 216 with which the tool is adaptedto operate includes a plurality of fasteners 217 which are maintained ina predetermined spaced relation by the supporting strip. The proposedstrip, which has been indicated will be disclosed in a co-pendingapplication, envisages a series of plastic carrying means fororientation of the fasteners with the head portions of the carryingmeans being interconnected. After a series of fasteners have been fired,the carrying means or strip, will be ejected forwardly through theaperture 272. At times, when spacing of the environment are tight, it isnecessary to dispose of the strip and hence a cut-off mechanism has beenprovided. The detector blade 270 is provided on opposite upper sides ofthe aperture 272 with a pair of depending knives 360 having knife edges361. The back surface of each knife 360 is coplanar with the surface ofblade 270 riding on the front surface 31 while the front surface of eachknife 360 is tapered to intersect said back surface and provide thecutting edge 361. The detector blade levers 310 and 312 include upperextensions 362 and 364 respectively which extend upwardly and rearwardlyfrom the pivots 318 and 334. For operation of this device, a manuallever 370 is mounted on body 250 and provided with a pair of arms 372,374 pivoted centrally thereof at 376 and having cammed surfaces 378 and380 at their respective far extremities. The lever 370 is provided witha yoke connecting portion 382 at its upper extremity forming a handlefor manual engagement by the operator. A pin 384 is positionedinternally of the handle 254 of casing 250 and a similar pin 386 extendsbetween arms 372 and 374, intermediate the extremities of lever 370. Atension spring 388 extends between the pins 384 and 386 and maintainsthe lever 370 and its associated cam surfaces 378 and 380 out of contactwith the upper portions 362 and 364 of detector blade levers 310 and 312with pin 386 serving as the stop means which by engaging with case 250serves as the lever orientation means. Depressing lever 270 byapplication of a force to the handle 382, pivots the lever 370 aboutpoint 376 to bring the cam surfaces 378-380 into engagement with theundersurface of the upper portions 362 and 364 of the lever arms 310 and312. The bulbous connections 316 and 332 at the opposite end of thelever arms then act on the lugs 278 to move the detector bladedownwardly against spring 292, as viewed in FIGS. 2 and 8, to bring theknife edges 361 into engagement with the collated strip of the typeshown in phantom shown in FIG. 2, to sever the used portions of thestrip extending outwardly through the aperture 272. Release of pressureon handle 382 permits the spring 388 to move the lever 370 back to itsposition of rest, and spring 292 to return the blade 270 to its normalposition of rest.

FEED MECHANISM As has been previously discussed, the collating means 216for the fasteners adapted to be used with this embodiment of power toolincludes plastic members which are joined at their head and havelaterally extending flange means and body means depending from saidheads. At the base of the body shell 250, there is provided a guide railmeans 400, see FIGS. 2, l2 and 13, which includes a grooved casting 402having a downwardly opening slot 404 extending the longitudinal lengthof the casting 402. The slot 404 includes lateral grooves 406 which arealigned with and complimentary to the grooves 204 in the nose piece.Suitable flange means 408 are provided to accept fasteners 410 formounting the casting relative to the body 250. The collated strip 216 isinserted from the back end of the slot 404, opposite nose piece 190, theheads of the strip riding in the grooves 406 and the body portionsdepending downwardly, as shown in phantom in FIG. 2.

The feed mechanism includes advancing means for sequentially advancingindividual fasteners into position under the hammer 112. Referring toFIGS. 2, 13 and 14, the advancing means include fingers means 420consisting of a pair of narrow sheet metal members 422 interconnected bya flange 424. An abrupt shoulder 426 is formed at the free end of eachof the members 422, while the undersurface thereof includes a doubletapered cam surface designated at 428 and 429. At the opposite extremityof the finger means 420 and connected to flange 424, is an upstandingapertured flange 430 having a central aperture 432. Each of the fingermeans 420 include oppositely disposed apertures 434 which are inregistry with one another and are positioned adjacent the end carryingflange 430.

A rod 440 is mounted at one end 442, in the casing 250 by suitablemeans, such as screw threads or welding, and extends cantilever fashioninto the interior of the case 250. Rod 440 has mounted thereon acompression spring 444. The spring 440 normally occupies substantiallythe entire length of rod 440. The aperture 432 of flange 430 of thefinger means 420 is positioned on the free extremity of rod 440 andmoved to the right, as viewed in FIG. 2, to compress the spring 444. Itwill be noted that the casting 402 at the end 403 adjacent its juncturewith the nosepiece 190, is milled away to expose the groove 406 to theends 426 of the finger means 420 The finger means 420 is pivoted aboutits aperture 434 and normally spring urged downwardly to the left by theweight of the finger means and the spring 444.

A double yoke member 450 is pivoted on pin 376 and provides a pair ofarm members 452 extending downwardly and embracing the finger means 420.A pivot pin 454 connects the pivot aperture 434 of the finger means andsuitable aperture means in the yoke arms 452. It should be noted thatthe aperture 432 in the finger means, is slightly larger in diameterthan the rod 440 so that movement of the yoke arms 452 in a direction tothe left in FIG. 2 will always permit the finger means 420 to dependdownwardly into the groove 406 of the track 400 and the groove 204 inthe nose piece 190. It should be noted that the spring 444 has apredetermined strength for urging the finger means 420 in the directionto the left toward the nose piece. To control the advancing means, theyoke has a second pair of arms 456 extending upwardly opposite the arms452. The arms 456 have a cam surface 458 on their rear edge abutting thespring urged stop means 460 which has a strength substantially from fourto six times greater than that of power spring 444. The stop means 460includes a cavity 462 in the body 250, a spring 464 and a cap-likeplunger 466 which is freely slidable within cavity 462 and inencompassing relation to spring 464. Plunger 466 acting against the camsurfaces 458 of the yoke 450, tends to urge the finger means 420 in thedirection to the right since spring 464 is many times stronger than thepower spring 444 and thereby overcomes the force of spring 444.

To overcome the stop 460 a piston 470 is provided in opposition to theplunger 466. A cylinder 472 is threadedly mounted in the port 64 andaccess provided to the bore 60 carrying the power fluid. Suitable sealmeans 474 is provided within the cylinder 472 acting against a stop 476.The piston 470 is so dimensioned that it abuts plunger 466 with one endat all times and in the retracted position, shown in FIG. 2, is seatedon a shoulder 478 at its end opposite the plunger 466, therebycontrolling the relative movement of plunger 466 in an outward ordirection to the left.

The operation of the feed means is as follows: When the trigger 350 issqueezed, detector blade 270 is moved to actuate switch 340, power fluidis introduced through the tube 260 into bore 60. Power fluid then flowsfrom port 64 into the cylinder 472 and movement of the piston 470overrides the spring 464 by moving it to the right, as viewed in FIG. 2.By removal of stop means 460 the power spring 444 is permitted to actupon the flange 430 and attempt to move the finger means 420 to theleft. The power piston in its lower or extended position provides a stopmeans against which the end of the collated strip can come to rest or,as is shown in FIG. 2 in phantom, the hammer portion 112 projectsthrough the interior of one portion of the collated strip and preventsmovement thereof until, during the power cycle, the power piston 100 isretracted. When the hammer 112 in its upward movement clears thecollated strip, the abrupt shoulder 126 engages a complementary shoulderin the strip and moves it forward with a rocking ofthe yoke 450 as shownin phantom. The collated strip has a series of notch-like grooves foracceptance of the shoulder means 426 of the finger 420 and the stroke ofthe finger means is controlled by the movement of the yoke 450 until ittouches the plunger 466 in retracted position. This is a calculatedposition to insure proper positioning of the collated strip beneath thepower piston. When the cycle is complete, the fastener is driven throughthe collated holder into the work structure and the power fluid is thenevacuated through the tube 260. This permits the piston 470 to return toits seated position against shoulder 478 and the spring 464, being muchstronger than spring 444, swivels the yoke 450 to the solid lineposition shown in FIG. 2, thereby retracting the finger means with thecam surfaces 428-430 riding across the upper surface of the collatedstrip 216 until the shoulder means 426 engage the next notch in thestrip. The feeding means is then ready for recycling.

It will be noted in FIG. 13 that the body shell 250 is open on the leftside and bottom to provide access to the interior. A thin sheet metalcover 500 is used to cover the interior of the body shell 250. Cover 500has at one extremity, an inwardly and thence upwardly directed bottom ornose portion 502 which protects the strip of collated fasteners fromdamage as they are moved along the grooves 406. The upwardly turnedportion 504 terminates in spaced relation to the rail casting 402 toprovide a slot 506 which permits the operator to move independent orshort sections of collated fasteners along the guide rail. It will berecognized, of course, that power means such as a spring, could be usedfor this purpose, but it has been found unnecessary when access is soreadily available through the slot 506.

Thus, it will be apparent to those skilled in the art, that aneconomical, high velocity, high force, power source is combined with asimple, fail-safe positive positioning ofa collated strip of fastenersfor driving into a work structure. The safety features, such as adetector blade when mechanically moved, provides a circuit actuatingmeans for remotely controlling the reservoir and pump used forintroducing the power fluid into the power device.

We claim:

1. A feed mechanism for advancing a collated strip of articles apredetermined distance including track means adapted to support saidstrip, movable first stop means for interrupting movement of said strip,advancing means for moving said strip when said first stop means isremoved from the path of travel along said track, power means foractuating said advancing means, second movable stop means forcontrolling actuation of said advancing means said predetermineddistance, the advancing means including a pair of finger membersconnected by suitable means in spaced relation, the finger membersoscillating said predetermined distance from an initial position to asecondary position and back to said initial position, the finger membersincluding protuberance means at one end engageable within complementaryrecesses in said strip, said protuberance means including an abruptshoulder on the edge facing the direction of the advancement of saidstrip to said secondary position and a cam surface to retract saidprotuberance from the strip recess when said finger means is retractedto said initial position, apertured support engaging means spaced fromsaid protuberance means and including an apertured flange integral withthe connecting means and adapted to accept rod-like support means insliding relation for rectilinear movement along said support means, saidpower means including a compression spring encircling said rod-likemember and normally biased against said flange to urge the fingers intocooperation with said strip and said strip towards said first stopmeans.

2. A feed mechanism of the type set forth in claim 1 wherein said secondstop means is movable from a first position to a second position, meansconnected to said finger means engageable with said second stop meansand adapted to permit movement of said fingers from said initialposition to said secondary position when said second stop means hasmoved to its second position.

3. A feeding mechanism of the type set forth in claim 2 wherein saidconnecting means is a lever pivotally supported intermediate its lengthand pivotally connected to said fingers adjacent one end, said leveradapted to bear on said second stop means adjacent its opposite end.

4. A feeding mechanism of the type set forth in claim 2 wherein saidmovable second stop means includes a spring urged member stronger thansaid power means and adapted to normally urge said fingers to theirinitial position, means to override the spring of said second stop meansand to move the stop means to its second position whereby said powermeans can operate said fingers and strip toward said first stop means.

5. A feeding mechanism of the type set forth in claim 4 wherein removalof the overriding force against said second stop means permits thespring of said second stop means to overpower the finger advancing powermeans and return the fingers to their initial position.

6. A feeding mechanism of the type set forth in claim 5 wherein theoverriding force against said second stop means is a pressure actuatedplunger, the pressurized medium acting on said plunger also providingthe motivating force for the movement of said first stop means.

1. A feed mechanism for advancing a collated strip of articles apredetermined distance including track means adapted to support saidstrip, movable first stop means for interrupting movement of said strip,advancing means for moving said strip when said first stop means isremoved from the path of travel along said track, power means foractuating said advancing means, second movable stop means forcontrolling actuation of said advancing means said predetermineddistance, the advancing means including a pair of finger membersconnected by suitable means in spaced relation, the finger membersoscillating said predetermined distance from an initial position to asecondary position and back to said initial position, the finger membersincluding protuberance means at one end engageable within complementaryrecesses in said strip, said protuberance means including an abruptshoulder on the edge facing the direction of the advancement of saidstrip to said secondary position and a cam surface to retract saidprotuberance from the strip recess when said finger means is retractedto said initial position, apertured support engaging means spaced fromsaid protuberance means and including an apertured flange integral withthe connecting means and adapted to accept rod-like support means insliding relation for rectilinear movement along said support means, saidpower means including a compression spring encircling said rod-likemember and normally biased against said flange to urge the fingers intocooperation with said strip and said strip towards said first stopmeans.
 2. A feed mechanism of the type set forth in claim 1 wherein saidsecond stop means is movable from a first position to a second position,means connected to said finger means engageable with said second stopmeans and adapted to permit movement of said fingers from said initialposition to said secondary position when said second stop means hasmoved to its second position.
 3. A feeding mechanism of the type setforth in claim 2 wherein said connecting means is a lever pivotallysupported intermediate its length and pivotally connected to saidfingers adjacent one end, said lever adapted to bear on said second stopmeans adjacent its opposite end.
 4. A feeding mechanism of the type setforth in claim 2 wherein said movable second stop means includes aspring urged member stronger than said power means and adapted tonormally urge said fingers to their initial position, means to overridethe spring of said second stop means and to move the stop means to itssecond position whereby said power means can operate said fingers andstrip toward said first stop means.
 5. A feeding mechanism of the typeset forth in claim 4 wherein removal of the overriding force againstsaid second stop means permiTs the spring of said second stop means tooverpower the finger advancing power means and return the fingers totheir initial position.
 6. A feeding mechanism of the type set forth inclaim 5 wherein the overriding force against said second stop means is apressure actuated plunger, the pressurized medium acting on said plungeralso providing the motivating force for the movement of said first stopmeans.